Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$63.34	11.323%	$70.512	$70.51	$70.50	$70.50
Purchase #2	$41.81	9.804%	$45.9091	$45.91	$45.90	$45.90
Purchase #3	$10.52	8.144%	$11.3767	$11.38	$11.40	$11.40
Purchase #4	$57.75	7.646%	$62.1656	$62.17	$62.15	$62.20
Purchase #5	$245.25	8.229%	$265.4316	$265.43	$265.45	$265.40
Purchase #6	$192.93	10.387%	$212.9696	$212.97	$212.95	$213.00
Purchase #7	$90.60	10.807%	$100.3911	$100.39	$100.40	$100.40
7 purchase totals =	$702.20		$768.7557	$768.76	$768.75	$768.80